Abstract

Due to the rapid growth of the composite market, several European laws have emerged to minimize their environmental impact (EU 2000/53 / EC, End of life vehicles), as well as to make rational use of landfills (EU 1999/31 / EC). For example, in the aeronautical sector, composites can reach 50% by weight of the aircraft. Consequently, recyclability is a key issue. The objective of this work is the study of the recycling techniques of carbon fiber composites with thermoset polymer matrix in order to obtain fibers with similar properties to the original ones. In this way, the fibers could be reused in new composites by themselves or together with flass fibers in the manufacture of new hybrid composite materials. By this hybridization, materials with properties far superior to the GFRP would be obtained, but at much lower cost than the original CFRP. Therefore, this recycling and reprocesing strategies provides great economical attractiveness.  The main objective of the project is to study and optimize the recyclability of cured carbon fiber / epoxy prepregs for use in hybrid materials. Starting from a pyrolysis in a controlled atmosphere reactor, followed by a oxidation, carbon fibers with properties similar to virgin fibers are obtained, with a loss less than 20% of the tensile strength. An evaluation of the different parameters of the recycling process has been carried out in order to optimize the procedure. The characterization of the fibers includes tensile tests, scanning electron microscopy and Raman spectroscopy.

Abstract

In terms of energy, the Earth is an open system: it constantly receives energy from solar radiation and emits the same amount of energy in the form of more degraded radiation; the displacement of the equilibrium point between these two flows due to the growth of greenhouse gases, increases the average temperature of the Earth and causes climate change. On the other hand, in relation to matter, the Earth is a closed system, apart from the sporadic fall of some meteor. Nature has the ability to regenerate the organic materials of living beings but not with many other materials.

Today, the volume of materials involved in human activities is 12.5 tons per person per year (1.5 to 4 times more in rich countries): 25% of the total comes from biomass (including food), 15% are fossil fuels, 10% are metal ores, 42% are other minerals (mainly for construction) and 8% are recycled. On the other hand, obtaining and transporting materials worldwide requires more than 40% of the energy of the human system, a value that is growing with the use of increasingly rare, scarce and dispersed materials. The overexploitation of resources coupled with the increasing use of non-renewable energy resources (fossil fuels and uranium), with the consequent energy and climate crisis and the deterioration of the environment, leads both to a change in the energy model and to rethinking the practices today dominant of continuous economic growth and the linear economy based on extract-use-throw.

The purpose of this communication is, after presenting the figures on the global metabolism of materials, to reflect on some of the new attitudes and actions that will need to be adopted within the framework of sustainable development. By way of example, the following are cited: 1) Moderate, reduce, eliminate the use of materials where possible; 2) Extend the life of goods and material infrastructures; 3) Reuse, recover, recycle materials; 4) Return as much as possible biologically based materials, more recyclable; 5) Avoid, as far as possible, technologies based on rare or scarce materials; 6) Avoid the dispersion of materials in the environment (atmosphere, water, soil); 7) Encourage the use of local materials in order to minimize transport and its energy impact; 8) Take care of the quality and good health of basic resources: air, water and fertile soil.

Abstract

This work presents ionically vulcanized carboxylated nitrile rubber (XNBR) compounds reinforced with conventional and sustainable fillers. The impact of adding traditional fillers, such as carbon black and silica, as well as sustainable options, such as cellulose and ground tire rubber from end-of-life tires (GTR), on the rubber's mechanical, thermal, self-healing, and recyclability properties is carefully analyzed. The results demonstrate that the incorporation of sustainable fillers achieves a favorable balance between repairability, recyclability, and mechanical performance. In particular, the compound with GTR exhibits reinforcement levels comparable to those of silica-based compounds, while maintaining full reprocessing and repairability. This study highlights the potential of using sustainable and recycled materials in the rubber industry, significantly contributing to the development of environmentally friendly elastomeric compounds.

Abstract

This PART 2 is the continuation of the project: “PART 1: recyclability and revalorisation of railway components made of composite materials”. Following the successful development of the recycling process for the Lightweight Running Gear Frame prototype and the formulation of a 3R epoxy resin suitable for use in the railway sector, the project advances with the following challenges:

1. Revalorisation of Recycled Carbon Fibre (rCF) into new fabrics, by obtaining hybrid rCF and polyamide 6 (PA 6) yarns by adapting and optimising textile processes to incorporate recycled fibres into new intermediate products.
2. Production of a new prepreg and its laminates. The new prepreg and its laminates will be produced using the dry fabric obtained in the previous objective and the 3R epoxy resin, developed in PART 1 of the project.

The overall conclusions of the project are that: the recycling process is suitable for post-consumer components, the spinning and weaving methods are effective for dealing with this type of fibres and the 3R laminates manufactured are of high quality and ready to be evaluated in terms of their properties.

Abstract

One of the main areas of study within composite materials, and more specifically within the aerospace sector, is their recycling. Currently, most composite waste management techniques involve the disposal of these materials without the possibility of reuse. This work presents the use of a hydrothermal process that enables the recovery of carbon fiber fabrics from a composite laminate in a condition suitable for use in new manufacturing processes.

In this study, different types of carbon fiber reinforcements (dry fabric, non-crimp fabric and prepregs) were used to manufacture laminates, which were subsequently subjected to a hydrothermal recycling process. The treatment conditions were optimized for each material studied, achieving resin removal rates above 90% for several of them. Moreover, the fibers obtained from the hydrothermal process preserved their original structure, allowing them to be handled and reused for the manufacture of new laminates. It was also verified that the process did not remove the fiber sizing.

A testing campaign was carried out to evaluate the mechanical properties of the recycled material, and the results were compared with those obtained from the original samples. The findings show that the recycled fibers could be reused. Although their application in primary aircraft structures may be debatable, they could be employed in other components with lower performance requirements. An example of such use is their application in drone manufacturing, as demonstrated in the final phase of the RECICOM project.

The work presented in this abstract is part of the RECICOM project, funded by the European Union through Next Generation funds and by CDTI under its PTA2022 program – SME Category.

Abstract

In an attempt to cover the needs and requirements of consumers, packaging without good recyclability is sometimes introduced in the market. This is more evident in the case of polyethylene terephthalate (PET). PET is a highly recyclable material that results in a recycled product with enhanced quality. However, there are other type of PET multilayered packaging that are being introduced in the market. These packaging products include additional materials such as other type of polymers, metals, paper, etc., as well as different type of pigments, colouring agents and impurities confering a critical colour to the packaging. When this new packaging arrives to the recycler it generates problems, resulting in low quality products or even rejected, being deposited in landfill. This implies an important environmental reduction (mainly in the CO2 emissions) and in the economic affairs. For this reason, the recycling companies and, in general, waste management companies, are interested in alternatives that allow these residues to have a viable outlet. This development is presented as a solution to the problem of these particular PET multilayered residues. The main objective is the industrial development of thermosetting resins (alkyds and unsaturated polyesters) that include in their composition materials obtained from the chemical recycling of these multilayered packaging, at an affordable price and with reduced environmental impact.

Abstract

In the railway sector, represented by TALGO, there is growing concern about the recyclability and reusability of composite parts at the end of their useful life. To address this concern and comply with Spanish and European directives and legislation, an innovation project (divided into "PART 1" and "PART 2") has been carried out in which AITEX, CIDETEC, iTREE, and TALGO have collaborated. The main results of the first part are as follows:

1. Recycling process of the composite material of the first prototype of the Lightweight Running Gear Frame: This process focuses on recovering the carbon fiber contained in the material by combining several chemical-physical steps.
2. Development of a 3R (recyclable) epoxy resin formulation: This resin meets the thermal, mechanical, and FST (Fire, Smoke, and Toxicity) requirements of the railway sector and is suitable for use with prepreg technology.

The results indicate that the recycling process is suitable for producing post-consumer parts and that the formulated resin meets the required standards. The overall conclusions of the project will be revealed in PART 2 of this study.